Field of the Invention
The present invention relates to an object information acquiring apparatus and a control method therefor.
Description of the Related Art
In optical imaging that irradiates light on an object such as a living body from a light source such as a laser, the inside of the object information obtained on the basis of the incident light have been in progress actively in the medical field. As a kind of this optical imaging technique, there is photoacoustic imaging (PAI). In the photoacoustic imaging, a tissue that absorbs the energy of pulse light and generates elastic waves. The elastic waves propagated in the object and are received. Characteristic information relating to the inside of the object is imaged on the basis of a reception signal of the elastic wave.
When light is irradiated on the object in the photoacoustic imaging, since there is a difference in light absorption coefficient between high absorption area (a tumor of a living body etc.) and the other tissues area, the high absorption area, from the light energy instantaneously expands to generate an elastic wave. Characteristic information is obtained by subjecting a signal obtained by receiving the elastic wave with an acoustic receiver to analysis processing. The characteristic information is optical characteristic value distributions such as an initial sound pressure distribution, a light absorption energy density distribution, and a light absorption coefficient distribution. By measuring these kinds of information by selecting various wavelengths, the information can also be used for quantitative measurement of specific substances (hemoglobin concentration in blood, oxygen saturation in blood, etc.) in the object.
In order to accurately calculate these kinds of characteristic information, it is desired to receive, from the entire circumference, elastic waves three-dimensionally generated in the object and reconstruction an image using reception signals of the elastic waves. However, in most cases, because of physical limitations between the acoustic receiver and a measurement segment, it is difficult to receive the elastic waves from the entire circumference. As a result, since characteristic information is estimated from limited reception conditions, noise such as data omission and a reconstruction artifact occurs in imaged characteristic information. Therefore, in order to avoid this problem, Japanese Patent Application Laid-Open No. 2010-088497 proposes to perform acquisition of photoacoustic waves a plurality of times in different positions, reconstruction an image with respect to reception signals, and acquire characteristic information. The image reconstruction means processing for allocating (projecting) an arbitrarily extracted reception signal (or a projection signal obtained by arbitrarily subjecting the reception signals to processing such as weighting) to reconstruction pixels (voxels).